(1) Field of the Invention
The invention relates to a modification of a standard double-disk refiner used to mechanically pulp wood to fiberous form for subsequent production of paper products.
(2) Description of the Prior Art
Conventional disk refiners used for production of mechanical pulp are of two general types-single an double rotating disks. (Gavelin, N. G. 1966. Science and Technology of Mechanical Pulp Manufacture. Lockwood Publishing Co., Inc., New York, N.Y.).
In a double-disk refiner, two solid disks are rotated at constant speed in opposite directions on separate horizontal shafts. The speed of rotation varies from about 1500 rpm to 1800 rpm. Total installed horsepower on each shaft may be as great as 5000 and the diameter of disks may be as large as 52 inches. Woody material to be pulped in the form of wood chips or fiber is fed to the center of the disks via a screw conveyor. The refining zone may or may not be steam pressurized. Each refining disk contains a number of cast alloy plates which form the refining surface. A pattern, usually consisting of a series of bars and grooves, are cast into the surface of the plate to effect varying degrees of refining action.
In the mechanical pulping process, whole green wood bolts are first reduced to chips about 1-inch along the grain. (Sawdust, planer shavings, and other waste material may also be used, but green wood is preferred.) The chips are then washed to remove dirt and other undesirable materials. From the chip washer, chips may be processed directly in a first stage refiner or may go to a screw-press for initial disintegration, heating, pitch removal, and sometimes mild chemical impregnation. First stage refining may be followed by either one or two additional refining stages prior to screening for removal of oversize particles, bleaching, and sheet formation.